Researchers at the University of Maryland in College Park, Maryland, have discovered a way to use a “Josephson Junction” to entangle quantum bits. Project leader Fred Wellstood claims that his team has proven that “you could use Josephson Junctions to build a quantum computer.” In the early 1960s, a British graduate student in physics named Brian Josephson found that electrons in a superconducting material could tunnel through an insulator. He later received the Nobel Prize for his discovery. The technology of Josephson Junctions has been proposed to make ultra-fast and efficient computers. In the 1960s and 1970s IBM invested billions in Josephson Junction technology, but abandoned the project in 1983 after making little progress. More recently, a researcher named Konstantin Likharev has proposed making a superconducting petaflops computer with 100GHz superconducting CPUs. Although researchers in the fields of quantum physics and superconducting have made bold claims about superfast computers, we should not hold our collective breaths waiting for breakthroughs. Josephson Junctions are difficult to fabricate, only operate at cryogenic temperatures, and do not offer performance much better than what future silicon CMOS chips can achieve. Although quantum computing has made numerous advances in the last decade, it is unlikely that quantum computing will ever be more than a niche technology.

USER COMMENTS 81 comment(s)

Bit pessemistic…(8:02am EST Fri May 23 2003)…of you is it not? These things all start slow and cumbersome. When the manufacturing technology improves and operating temperatures rise, this could be the way forward.

And…. 1ST POST WOOOOOO I RULE (and so forth) – by -)

Lest we forget…(9:47am EST Fri May 23 2003)that the first PC was the size of a gymnasium. It didn't evolve overnight. – by 2nd post is better!

…will ever be more than a niche technology.(9:52am EST Fri May 23 2003)And those huge rooms full of bulbs and all kinds of doohickeys will never advance very far either…these newfangled “computers” are gigantic montrosities that take up entire rooms and buildings just to perform basic tasks…

To the moon? Ha…that Jules Verne character is a nutjob. To the moon? What's he gonna say next? Boats that go under the sea? HA!!!

Automobile? I'd never trust myself in one of those things…just me and my trusty old horse and nothing more. Besides how are you going to get the thing to move? There are more than 5 “gas stations” in all of New York…

all things at some point are proposterous and unable to be achieved. Saying quantum computing will be a niche thing I believe is a bit short sighted. In time…as long as we humans are still on this planet, we will create machines that will easily fly in and out of space and transport large numbers of people (a la Star Trek) and built into the very fabric (steel? aluminium? something i dont know) of those machines we will have more computing power than we have on the entire planet now. We wil monitor every surface and every reaction that occurs wintin the machine. it may be incomprehensible to believe now…but people have thought of far more…and we have done it.

Heh(11:07am EST Fri May 23 2003) Konstantin Likharev has proposed making a superconducting petaflops computer with 100GHz superconducting CPUs.—Yeah but how fast does this run Doom3 ? – by kz

Yeah But…(11:45am EST Fri May 23 2003)Linux can do that to! – by 2cent

Famous quotes(11:56am EST Fri May 23 2003)“it is unlikely that quantum computing will ever be more than a niche technology”

“Theres only likely to be a market for ten of these things”

and who could forget

“640k is enough for anyone”

Look its not going to be a matter of if but a matter of when ::) – by Lint

If or When, the real question should be…(12:40pm EST Fri May 23 2003)Should we? Are we really moving forward with the intent of doing it right?

For years we could create really well working concepts, and other ideas, that work well on a small scale. Processors and Programs that are well built, fast, efficiant, and small is what we need. 110 million transistors is great, but is there waste?? Are we doing things that don't need to be done on the chip?? YES!!!!

And programming – how disgusting can code get???? Please – slow down and optimize what we currently have!!! How much more and better systems could we have if we would sit down with the engineers and clean it up.

Then again, that would slow down developement and who wants to do that. Screw it, I like running only slightly faters on a system that will convert to Lava without liquid cooling!!!

– by Kafka

'scuse me ?(1:31pm EST Fri May 23 2003)How can you write:“The technology of Josephson Junctions has been proposed to make ultra-fast and efficient computers….recently, a researcher named Konstantin Likharev has proposed making a superconducting petaflops computer with 100GHz superconducting CPUs”and conclude:“we should not hold our collective breaths waiting for breakthroughs. Josephson Junctions…do not offer performance much better than what future silicon CMOS chips can achieve.”

Anyone remember?(2:59pm EST Fri May 23 2003)'The market for computers will consist only of the 5 richest kings of Europe'

and

'640k aughta be enough for anyone.'

(Probably not word for word correct but yea o.o )

I cant remember who said the first one o.o but the second one was from none other then Billy G himself o.o – by Elorien

Only one critical technology away, actually…(4:47pm EST Fri May 23 2003)Solid state, compact cryostats that are thermodynamically efficient. The chief problem with Peltiers is that they're nowhere near as efficient as vapor-phase (“refrigeration/freon”) systems. And vapor phase systems are pretty good, but nowhere near the reverse Carnot cycle limit.

And worse, “pumping the heat out” of something that is cryogenic in temp requires orders of magnitude more energy to bring it to “room temp” for dissipation. You'd be surprise how much electricity is required to chill down a liter of liquid nitrogen, which is a nice warm 80°K or so. Liquid helium takes 100x the energy to lower it to 4°K … as I remember it, it is something along the lines of (hot/cold)^1.5 …

So, lets work backwards. (300/5)^1.5 = 500 in round numbers. Therefore, every watt of waste heat at 4°K if pumped up to warm room temp (300°K) for disposal, would turn into about 500 watts of waste heat. That's one hell of a power bill, if the chip actually requires more than 1 watt of electrical energy itself.

Don't remind me that superconducting chips by definition have no resistive losses. True, but they do dissipate heat: as the quanta whizz through the crystal lattice, they induce phonons (not photons), a kind of quantum noise, into the lattice. Ultimately, phonon noise dissipates as heat.

Again, if we just had good, solid-state cryostats that could get down, in stages, to 4-10°K, then superconduction would be on every desktop. Milliwatt chips would be able to do amazing things, I do think.

– by GoatGuy

Quantum Computing being a niche product?(4:02pm EST Sat May 24 2003)How did you manage to draw that conclusion from that little passage?

I'd agree that superconducting computers, for the time being at least, are in the realms of academia only. But trust me, the second that someone can mass-produce a quantum computer, and the method to keep it functional (which may include some solid-state cryostats :)), they will become the mainstream.

To me it sounds like saying “they'll never use these new fangled transistors over good old valves. Who ever heard out of making a computer out of *silicon*?” – by Sev

Solid state cryostats hmmm(4:18pm EST Sat May 24 2003)Thin film TEs are the key I think Mr. GoatGuy, just like they did at the Research Triangle in NC, with bismuth telluride and antimony telluride.

I do wonder if it is worthwhile to try improving the phonon transfer between the two semiconductors? I would think there has got to be a way to better align the two lattices or to make some holes or provide fillers to trick the lattices into a more perfect alignment. Maybe a mild sqeeze down rather than an abrupt change to let the phonons through.

My gut tells me you gotta give the phonons a clear path at the junction or they will collide into chunks of the disimilar lattice, reducing efficiency.

As far as using them as they are, seems you could manufacturer a pretty good stack to begin with. To add more stacks, coat the hot side of the TE with buckyballs, they seem to have great heat transfer ability, or maybe a layer of some nanotubes running coolant, then your next TE and so on and so on..

80°K is so much easier than 4-10°K. You think boot up times are bad now, try for a 3-4 hour cool down before your quantum PC is ready to run.

What do you think of adiabatic demagnetization refrigerators? Seems they would destroy a quantum computer. – by Zeke

TE (thermoelectrical effect) …(1:35pm EST Sun May 25 2003)Z –

TE, whither Bismuth Flangeride based or Zirconium tellmemoruride based … :-) suffer from having an oversized Achilles heel: their 'Z' efficiency decreases with decreasing temperature. Doh!

So in perspective, if a TE device is able to develop a 70° difference at 300°K, at 200°K, same device can only muster a 40° difference, and so on down the chain. You'd need a nearly infinite number of these puppies in sequence to get down to 4°-10°K range. And I would bet they'd be pretty inefficent.

Adiabatic demag? Good for copper, to get to nanokelvins. Not much good for bulk helium liquification. And oh, by the bye – we certainly would be using the helium route: only 4 known materials work at those temps: He, H, He-3 and D. The hydrogen line is pretty flammable, so it'd be He.

But then again, it all might (probably would NEED to) run in a vacuum. Especially if an ultra-high efficiency solid state “TE” type device come into play that can achive the sub decakelvin's needed for quantum computing.

I can't help but think(4:05am EST Tue May 27 2003)We are going in the wrong direction in computers.

A billion years of evolution, design by attrition, has produced a supercomputer that produces 15 watts of heat, the human brain.

While the human brain has quantum structures, it has no superconductive or vacuum structures.

Some would say that a protein based computer's instruction set is not capable of producing a general purpose computer. I would say that is true only if we adhere to conventional logic rules.

frustrating puzzle.

Goat, want to try for coffee or lunch sometime in the next 2 weeks? I'm back from Alaska and have some free time before summer session.

perdoatsonicdotnet

Been a while since I've been to Berkeley, but would not mind the hike.– by Perdo

Tiny TEM(5:41am EST Tue May 27 2003)Seems supperlattice TEs can't get close to the sub 10°K range. Not yet.

If you squeeze everything down in size, like quantum dots and nano wires, ZT goes up and you can get some coherence in the phonons. Might be some tricks to get them down the lattice and bunch up, and there would have to be some novel discovery.

Might be easier to make quantum computers that thrive on the chaos of room temperature than to make a cheap and efficient solid state cryostat for the finicky beasts. – by diddly